Recently, a variety of electronic apparatuses, such as videocassette recorders and personal computers, have been downsized and sophisticated. This trend requires lever switches used for detection to be more compact and slimmer as well as to work with reliability. The lever switches detect the presence or absence of recording media such as a tape or a disc, or detect an action of a mechanism in the apparatus. One of the conventional lever switches of this kind is disclosed in Japanese Utility Model Application Publication No. H04-27540.
This kind of conventional lever switch is described hereinafter with reference to FIG. 6 through FIG. 9. FIG. 6 shows a sectional view illustrating a structure of the conventional lever switch, and FIG. 7 shows a perspective view of the lever switch shown in FIG. 6. FIG. 8 shows a sectional view illustrating a structure when the lever switch shown in FIG. 6 is in operation, and FIG. 9 shows a schematic diagram illustrating that force is applied to the lever switch from behind, as shown in FIG. 6.
In FIG. 6, box-shaped housing 51 made of insulating resin has opening 511. Shaft 521 located at a middle section of lever 52 is rotatably held by housing 51. Driving section 522 on the lower face of lever 52 is accommodated in housing 51, while operating section 523 of lever 52 projects in a slanting position from opening 511 in an upward and leftward direction.
Common contact 53 and fixed contact 54 are both made from metal thin-plate, and they are disposed on the inner face of wall 560 (the lower wall in FIG. 6) opposite to opening 511. Both the contacts are bent over the edge wall 560 and extend outside housing 51. Common contact 53 having terminal section 531 and fixed contact 54 having terminal section 541 are thus formed.
Movable contact 55 is made from elastic metal thin-plate. A tip of first arm 552 extending from U-shaped bowing section 551 is urged elastically against common contact 53, while an intermediate section of second arm 553 extending from bowing section 551 is urged elastically against driving section 522 on the lower face of lever 52. A given clearance is provided between fixed contact 54 and contact 554 provided at the tip of second arm 553.
Lever 52 is held such that it can rotate on shaft 521 as a fulcrum in parallel with inner bottom face (rear inner face in FIG. 6) 570 of housing 51. Housing 51 thus accommodates common contact 53, fixed contact 54, movable contact 55 and parts of lever 52. The upper face (front face in FIG. 6) of housing 51 is covered by cover 580 shown in FIG. 7.
As shown in FIG. 7, the conventional lever switch discussed above is placed on wired-board 57 having plural wiring patterns (not shown), and terminal sections 531, 541 are soldered to a given wiring pattern. The lever switch is thus coupled to an electric circuit of an electric apparatus.
In the foregoing structure, operating section 523 of the lever is rotated by given force along direction A or B shown in FIG. 7. The lever can be directly rotated with operating section 523, or by using some pressing unit (not shown) on operating section 523 to work operating-section 523 within a given movable area. FIG. 8 shows the lever switch thus rotated.
In FIG. 8, since lever 52 rotates downward in the drawing on shaft 521 as a fulcrum, driving section 522 on the lower face of lever 52 urges movable contact 55 to bow, so that contact 554 at the tip of second arm 553 is brought into contact with fixed contact 54. Fixed contact 54 thus electrically contacts with common contact 53 via movable contact 55.
Release of the force applied to operating section 523 of the lever produces elastic restoring force of movable contact 55, so that driving section 522 is urged upward in the drawing, and lever 52 rotates upward. As a result, contact 554 leaves fixed contact 54 and returns to the status shown in FIG. 6.
However, the foregoing conventional lever switch has the following problem. Terminal section 531 of common contact 53 and terminal section 541 of fixed contact 54, both disposed on the inner face of wall 560, extend outside housing 51. Those terminal sections are soldered to wired-board 57 at only around wall 560 of housing 51. This structure thus invites the following inconveniences when extreme force F is applied to behind lever 52 as shown in FIG. 9, or extreme force F is applied to housing 51 from either side as shown in FIG. 7. The lever switch comes off from wired-board 57, or terminal sections 531 and 541 are deformed, so that operating section 523 of the lever moves outside the given movable area of the pressing unit (not shown) discussed previously. As a result, the lever switch sometimes does not work, or the operating force can be changed.